bug#18135: bug#3735: shell-mode editing, movement, and command entry broken by prompt/output changes

[miha]

Don Hopkins <don@donhopkins.com> writes:

> Thanks for looking into this! 
>
> I can’t reproduce the problem through that recipe, but weird things still 
> happen in other situations. 
>
> Try putting “ -la” in the kill buffer and then yanking it instead of typing 
> it at the end of the output of “echo ls”. 
>
> It totally ignores the whole line, as if you entered an empty line.
>
> But the thing that usually happens to me is that it enters the text that I 
> yanked, but I’m not sure what the exact conditions to trigger it are. 
>
> But at any rate, yanking “ -la” and hitting return should have the exact same 
> behavior as typing “ -la” and hitting return, so it’s probably caused by the 
> same underlying problem.
>
> I’ll let you know if I figure out other test cases that get it to enter the 
> text you yanked but not the text before that. It usually has something to do 
> with yanking text, possibly at the end or also in the middle of the line.

Reproducer:

- copy " -la" into kill ring
- type "echo ls" into M-x shell
- (Shell gives output line "ls".)
- Go up to output line "ls" (C-p).
- yank " -la"
- press C-b
- the line now "ls -la" with point after "l"
- press RET

Only " -la" is sent to the process instead of "ls -la"

This is because the 'field' text property of "ls" is 'output' but the
" -la" is inserted with insert-for-yank and doesn't have a 'field' text
property.

A similar thing happens if we insert a space using M-SPC
(just-one-space) in the middle of process output. The space is inserted
with 'insert' and doesn't inherit the 'field' text property of the
surrounding text.

This didn't cause a problem in older Emacs because the field text
property wasn't used yet at that time in comint.

I am willing to write up a patch to fix this. I'm thinking of having
comint-mode register a function in after-change-functions to mark text
inserted in the 'output' field as 'output'. Would this be okay or are
there any obvious flaws with this approach?

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